In JavaFX, the ImageView class represents a control that displays an image. You can use it to display an image loaded into an Image object, as shown in the following example:

import javafx.application.Application;
import javafx.scene.Scene;
import javafx.scene.image.Image;
import javafx.scene.image.ImageView;
import javafx.scene.layout.StackPane;
import javafx.stage.Stage;

public class MyJavaFXApp extends Application {

    @Override
    public void start(Stage primaryStage) {
        // Load an image from a file
        Image image = new Image("https://upload.wikimedia.org/wikipedia/commons/thumb/7/7e/Java_logo_icon.svg/1024px-Java_logo_icon.svg.png");

        // Create an ImageView object and set the image on it
        ImageView imageView = new ImageView(image);
        
        // Set the size of the ImageView
        imageView.setFitWidth(200);
        imageView.setFitHeight(200);
        
        // Create a StackPane and add the ImageView to it
        StackPane root = new StackPane(imageView);
        
        // Create a scene and set it on the stage
        Scene scene = new Scene(root, 300, 250);
        primaryStage.setScene(scene);

        // Show the stage
        primaryStage.show();
    }

    public static void main(String[] args) {
        launch(args);
    }
}

In this example, we create an ImageView object, and set the Image object that we created from a file as its content. We also set the size of the ImageView using the setFitWidth() and setFitHeight() methods, and add it to a StackPane object. Finally, we create a Scene object and set the StackPane object as its content, which is displayed on the screen.

You can also load an image directly into the ImageView object using its setImage() method, like this:

// Create an ImageView object
ImageView imageView = new ImageView();

// Load an image from a file and set it on the ImageView
imageView.setImage(new Image("file:myimage.jpg"));

Note that the ImageView object will automatically adjust its size to fit the dimensions of the image. If you want to display the image at a specific size, you can use the setFitWidth() and setFitHeight() methods, as shown in the example above.